1. Field of the Invention
This invention relates generally to hammer mills and particularly heavy duty hammer mills of the type used to break up discarded automobile bodies. The invention is specifically related to a replaceable, protective end cap assembly for the spider arm and more particularly to a side wall guard for the spider arm.
2. Description of the Prior Art
Hammermills of the type contemplated herein are widely used to reduce large metal objects such as cars into small fragments in a short time. This is of particular importance in reducing automobile bodies into manageable pieces for scrap recovery. These shredders generally include a housing, a hammer assembly mounted for rotary motion in the housing and a drive means for rotating the hammer assembly past grate bars which cooperate with the hammers to fragmentize or shred the metal objects.
It has been generally known that the life of the spider arms is limited due to the continuous impact of the end of the of the spider arms by the fragmentized metal. Repair of the spider arms requires a complete shut down and disassembly of the hammer mill before it can be returned to production. A complete shut down of the hammer mill can be costly not only for repair but also in loss of production time.
The life of the spider arms has been extended by the use of protective caps or tips which are mounted on the impact area of the face of the spider arms. It has, however, been found that the side walls of the spider arms are also subject to considerable wear from the flying metal pieces. The following patents describe various types of end caps that have been used to protect the face of the spider arms.
In the Francis Pat. No. 3,727,848 entitled "Hammer Mill with Replaceable Spider Arm Tips" issued Apr. 17, 1973, a protective tip or cap is described for protecting the nd of a spider arm. The cap in this patent includes a crescent shaped shroud portion which overlies the tip of the spider arm and a web portion which is positioned in a socket provided in the outer end portion of the spider arm. This type of cap has proven to be effective in protecting the tip of the spider arm however it does not protect the side walls of the spider arm.
In the Whitney Pat. Nos. 4,290,545 and 4,222,530 entitled "Replaceable Protective Means for End Disk of Shredder" issued Sept. 16, 1980 and "Method of Attaching A Protective Cap to a Shredder Component" issued Sept. 22, 1981, respectively, a replaceable protective cap is provided on the end disk of the rotary shredder assembly. The protective cap being formed of a wear resistant metal having a U-shaped configuration for covering the curved portion of the periphery of the end disks on the shredder assembly. The cap is described as including a dependent skirt which is designed to protect the interior areas of the end disk which are subject to wear. There is no provision for protecting the side walls of the spider arms in either of these patents.
The Hightower Pat. No. 3,844,494 entitled "Hammer Mill Rotor Assembly" issued Oct. 29, 1974, discloses a hammermill having heavy hammers mounted on the rotors forward of the centerline of the rotor. When the hammers are worn, they are moved to a pivot point on the center line of the rotor. The rotor is then cut down on the face and the sides to accomodate a replacable cap. The cap protecting the impact area both of the face and the sides of the rotor from wear. The cross sectional area of the spider arm is reduced in order to mount this cap on the spider arm. The cap is in the form of a unitary structure that is used to protect the rotor when the hammers are modified for movement to the center of the spider arms. This cap is made of a high strength steel and must be replaced in its entirety when it becomes worn or damaged.